The University of Laval in Canada recently compared the effects of two different dry period lengths on health and reproduction. The study, published in the July Journal of Dairy Science, featured 850 Holstein cows from 13 commercial dairy herds that were assigned to either a 35-day (short) or a 60-day (conventional) dry period, based on milk yield, number of calves and estimated calving interval.
Cows enrolled in the conventional dry period group were fed a dry cow ration from dry-off until 21 days pre-partum, at which time they were switched to a precalving ration. A pre-calving ration was fed to cows of the short dry period group throughout the entire shortened dry period.
• Dry period management did not affect culling rate for second-lactation cows, but a significantly higher culling rate occurred in multiparous cows with conventional dry periods compared to those with short dry periods.
• Lower incidence of metabolic disorders for second lactation, compared to third or later lactation cows in both groups.
• Cases of mild ketosis were lower for cows in the shortened dry period group.
• Occurrence of retained placenta was higher for second and later lactation cows in the short dry period. However, this did not lead to increased cases of metritis.
Researchers concluded that a short dry period can transition cows back to the milking herd sooner without major effects on health and reproduction parameters.